Optical record medium judging method and apparatus and focus servo controlling method and apparatus

Abstract

The distances from external surfaces to information record surfaces of the optical record mediums of various types are different from each other. An optical record medium judging method of judging the types of the optical record mediums is provided with the steps of: irradiating an information record surface of an optical record medium to be reproduced with a plurality of light beams to be focused on different positions on one optical axis; moving, so as to change a relative distance parallel to said one optical axis between an objective lens for prescribing focal points of the plurality of light beams respectively and the information record surface, the objective lens; receiving a plurality of reflection lights of the plurality of light beams reflected from the information record surface respectively, associated with a change of the relative distance; generating a plurality of focus error signals on the basis of the plurality of received reflection lights respectively; and judging a type of the optical record medium by comparing levels of the generated focus error signals respectively with a predetermined standard level.

What is claimed is: 
     
       1. An optical record medium judging method of judging types of optical record mediums, which distances from external surfaces thereof to information record surfaces thereof recorded with record information are different from each other, said method comprising the steps of: irradiating an information record surface of an optical record medium to be reproduced with a plurality of light beams to be focused on different positions on one optical axis;   moving, so as to change a relative distance parallel to said one optical axis between an objective lens for prescribing focal points of said plurality of light beams respectively and said information record surface, said objective lens;   receiving a plurality of reflection lights of said plurality of light beams reflected from said information record surface respectively, associated with a change of said relative distance;   generating a plurality of focus error signals on the basis of said plurality of received reflection lights respectively; and   judging a type of said optical record medium by comparing levels of the generated focus error signals respectively with a predetermined standard level.   
     
     
       2. A method according to claim 1, wherein: said optical record mediums comprise first and second optical record mediums which distances from the external surfaces thereof to the information record surfaces thereof are different from each other;   said irradiating step comprises the steps of irradiating the information record surface with a first light beam to reproduce the record information from said first optical record medium, and irradiating the information record surface with a second light beam to reproduce the record information from said second optical record medium, said second light beam having a focal point farther from said objective lens than said first light beam;   said receiving step comprises the steps of receiving a first reflection light of said first light beam reflected from the information record surface, and receiving a second reflection light of said second light beam reflected from the information record surface;   said focus error signal generating step comprises the steps of generating a first focus error signal on the basis of the received first reflection light, and generating a second focus error signal on the basis of the received second reflection light; and   said judging step comprises the steps of judging the type of said optical record medium as said first optical record medium if at least one of the levels of said first and second focus error signals is equal to or higher than the predetermined standard level, and judging the type as said second optical record medium if both of the levels are lower than the predetermined standard level.   
     
     
       3. A method according to claim 2, wherein, in said irradiating step, said first light beam is a 0 order light generated by a bifocal lens, and said second light beam is a +1 order light generated by said bifocal lens. 
     
     
       4. A focus servo controlling method of judging types of optical record mediums, on which record informations are recorded at linear velocities different from each other, and setting a focus servo gain and a focus servo frequency band corresponding to each of the types of said optical record mediums, said method comprising the steps of: irradiating an information record surface recorded with record information of an optical record medium to be reproduced with a plurality of light beams to be focused on different positions on one optical axis;   moving, so as to change a relative distance parallel to said one optical axis between an objective lens for prescribing focal points of said plurality of light beams respectively and said information record surface, said objective lens on the basis of a control signal;   receiving a plurality of reflection lights of said plurality of light beams reflected from said information record surface respectively, associated with a change of said relative distance;   generating a plurality of focus error signals on the basis of said plurality of received reflection lights respectively;   judging a type of said optical record medium by comparing peak values of the generated focus error signals respectively with a predetermined standard level;   setting the focus servo gain and the focus servo frequency band on the basis of the peak values; and   generating the control signal,   wherein the focus servo gain and the focus servo frequency band are set in said setting step by repeating following operations with respect to the linear velocities of said optical record mediums one after another: firstly, the control signal to move said objective lens at a moving speed corresponding to a fastest linear velocity among the linear velocities is generated by said control signal generating step;   the focus servo gain and the focus servo frequency band are set on the basis of a peak value of a focus error signal generated by moving said objective lens at the moving speed corresponding to the fastest linear velocity by said setting step, if the judged type of said optical record medium is one recorded with the record information at the fastest linear velocity;   secondly, if the judged type of said optical record medium is not one recorded with the record information at the fastest linear velocity, the control signal to move said objective lens at a moving speed corresponding to a second fastest linear velocity among the linear velocities is generated by said control signal generating step; and   the focus servo gain and the focus servo frequency band are set on the basis of a peak value of a focus error signal generated by moving said objective lens at the moving speed corresponding to the second fastest linear velocity by said setting step, if the judged type of said optical record medium is one recorded with the record information at the second fastest linear velocity.     
     
     
       5. A method according to claim 4, wherein: said optical record mediums comprise a first optical record medium, on which the record information is recorded at a first linear velocity, and a second optical record medium, on which the record information is recorded at a second linear velocity lower than the first linear velocity and which distance from the external surface thereof to the information record surface thereof is different from that of said first optical record medium;   said moving step comprises the step of firstly moving said objective lens at a first moving speed corresponding to the first linear velocity;   said receiving step comprises the step of firstly receiving the plurality of reflection lights associated with the change of said relative distance in said firstly moving step;   said focus error generating step comprises the step of firstly generating the plurality of focus error signals on the basis of the reflection lights received by said firstly receiving step;   said method further comprises the step of firstly calculating the peak values of the focus error signals respectively generated by said firstly generating step;   said judging step comprises the steps of judging said optical record medium as said first optical record medium if at least one of the peak values calculated by said firstly calculating step is equal to or higher than the predetermined standard level, and judging said optical record medium as said second optical record medium if all of the peak values calculated by said firstly calculating step are lower than the predetermined standard level;   said setting step comprises the step of firstly setting the focus servo gain and the focus servo frequency band on the basis of a highest peak value of the peak values calculated by said firstly calculating step, if said optical record medium is judged as said first optical record medium;   said moving step further comprises the step of secondly moving said objective lens at a second moving speed, which corresponds to the second linear velocity and which is lower than the first moving speed, if said optical record medium is judged as said second optical record medium;   said receiving step further comprises the step of secondly receiving the plurality of reflection lights associated with the change of said relative distance in said secondly moving step;   said focus error generating step further comprises the step of secondly generating the plurality of focus error signals on the basis of the reflection lights received by said secondly receiving step;   said method further comprises the step of secondly calculating the peak values of the focus error signals respectively generated by said secondly generating step; and   said setting step comprises the step of secondly setting the focus servo gain and the focus servo frequency band on the basis of a highest peak value of the peak values calculated by said secondly calculating step.   
     
     
       6. A method according to claim 5, wherein, in said irradiating step, said first light beam is a 0 order light generated by a bifocal lens, and said second light beam is a +1 order light generated by said bifocal lens. 
     
     
       7. An optical record medium judging apparatus for judging types of optical record mediums, which distances from external surfaces thereof to information record surfaces thereof recorded with record information are different from each other, said apparatus comprising: a light irradiating means for irradiating an information record surface of an optical record medium to be reproduced with a plurality of light beams to be focused on different positions on one optical axis;   a lens moving means for moving, so as to change a relative distance parallel to said one optical axis between an objective lens for prescribing focal points of said plurality of light beams respectively and said information record surface, said objective lens;   a light receiving means for receiving a plurality of reflection lights of said plurality of light beams reflected from said information record surface respectively, associated with a change of said relative distance;   a focus error generating means for generating a plurality of focus error signals on the basis of said plurality of received reflection lights respectively; and   a judging means for judging a type of said optical record medium by comparing levels of the generated focus error signals respectively with a predetermined standard level.   
     
     
       8. An apparatus according to claim 7, wherein: said optical record mediums comprise first and second optical record mediums which distances from the external surfaces thereof to the information record surfaces thereof are different from each other;   said light irradiating means comprises means for irradiating the information record surface with a first light beam to reproduce the record information from said first optical record medium, and irradiating the information record surface with a second light beam to reproduce the record information from said second optical record medium, said second light beam having a focal point farther from said objective lens than said first light beam;   said light receiving means comprises a first receiving means for receiving a first reflection light of said first light beam reflected from the information record surface, and a second receiving means for receiving a second reflection light of said second light beam reflected from the information record surface;   said focus error signal generating means comprises a first generating means for generating a first focus error signal on the basis of the received first reflection light, and a second generating means for generating a second focus error signal on the basis of the received second reflection light; and   said type judging means comprises a first judging means for judging the type of said optical record medium as said first optical record medium if at least one of the levels of said first and second focus error signals is equal to or higher than the predetermined standard level, and a second judging means for judging the type as said second optical record medium if both of the levels are lower than the predetermined standard level.   
     
     
       9. An apparatus according to claim 8, wherein, in said light irradiating means, said first light beam is a 0 order light generated by a bifocal lens, and said second light beam is a +1 order light generated by said bifocal lens. 
     
     
       10. A focus servo controlling apparatus for judging types of optical record mediums, on which record informations are recorded at linear velocities different from each other, and setting a focus servo gain and a focus servo frequency band corresponding to each of the types of said optical record mediums, said apparatus comprising: a light irradiating means for irradiating an information record surface recorded with record information of an optical record medium to be reproduced with a plurality of light beams to be focused on different positions on one optical axis;   a lens moving means for moving, so as to change a relative distance parallel to said one optical axis between an objective lens for prescribing focal points of said plurality of light beams respectively and said information record surface, said objective lens on the basis of a control signal;   a light receiving means for receiving a plurality of reflection lights of said plurality of light beams reflected from said information record surface respectively, associated with a change of said relative distance;   a focus error generating means for generating a plurality of focus error signals on the basis of said plurality of received reflection lights respectively;   a type judging means for judging a type of said optical record medium by comparing peak values of the generated focus error signals respectively with a predetermined standard level;   a servo setting means for setting the focus servo gain and the focus servo frequency band on the basis of the peak values; and   a control signal generating means for generating the control signal,   wherein said servo setting means sets the focus servo gain and the focus servo frequency band by repeating following operations with respect to the linear velocities of said optical record mediums one after another: firstly, said control signal generating means generates the control signal to move said objective lens at a moving speed corresponding to a fastest linear velocity among the linear velocities;   said servo setting means sets the focus servo gain and the focus servo frequency band on the basis of a peak value of a focus error signal generated by moving said objective lens at the moving speed corresponding to the fastest linear velocity, if the judged type of said optical record medium is one recorded with the record information at the fastest linear velocity;   secondly, if the judged type of said optical record medium is not one recorded with the record information at the fastest linear velocity, said control signal generating means generates the control signal to move said objective lens at a moving speed corresponding to a second fastest linear velocity among the linear velocities; and   said servo setting means sets the focus servo gain and the focus servo frequency band on the basis of a peak value of a focus error signal generated by moving said objective lens at the moving speed corresponding to the second fastest linear velocity, if the judged type of said optical record medium is one recorded with the record information at the second fastest linear velocity.     
     
     
       11. An apparatus according to claim 10, wherein: said optical record mediums comprise a first optical record medium, on which the record information is recorded at a first linear velocity, and a second optical record medium, on which the record information is recorded at a second linear velocity lower than the first linear velocity and which distance from the external surface thereof to the information record surface thereof is different from that of said first optical record medium;   said lens moving means comprises a first moving means for firstly moving said objective lens at a first moving speed corresponding to the first linear velocity;   said light receiving means comprises a first receiving means for firstly receiving the plurality of reflection lights associated with the change of said relative distance of said objective lens moved by said first moving means;   said focus error generating means comprises a first generating means for firstly generating the plurality of focus error signals on the basis of the reflection lights received by said first receiving means;   said apparatus further comprises a first calculating means for firstly calculating the peak values of the focus error signals respectively generated by said first generating means;   said type judging means comprises a first judging means for judging said optical record medium as said first optical record medium if at least one of the peak values calculated by said first calculating means is equal to or higher than the predetermined standard level, and a second judging means for judging said optical record medium as said second optical record medium if all of the peak values calculated by said first calculating means are lower than the predetermined standard level;   said servo setting means comprises a first setting means for firstly setting the focus servo gain and the focus servo frequency band on the basis of a highest peak value of the peak values calculated by said first calculating means, if said optical record medium is judged as said first optical record medium;   said lens moving means further comprises a second moving means for secondly moving said objective lens at a second moving speed, which corresponds to the second linear velocity and which is lower than the first moving speed, if said optical record medium is judged as said second optical record medium;   said light receiving means further comprises a second receiving means for secondly receiving the plurality of reflection lights associated with the change of said relative distance of said objective lens moved by said second moving means;   said focus error generating means further comprises a second generating means for secondly generating the plurality of focus error signals on the basis of the reflection lights received by said second receiving means;   said apparatus further comprises a second calculating means for secondly calculating the peak values of the focus error signals respectively generated by said second generating means; and   said servo setting means comprises a second setting means for secondly setting the focus servo gain and the focus servo frequency band on the basis of a highest peak value of the peak values calculated by said second calculating means.   
     
     
       12. An apparatus according to claim 11, wherein, in said light irradiating means, said first light beam is a 0 order light generated by a bifocal lens, and said second light beam is a +1 order light generated by said bifocal lens.